Neoproterozoic to Early Triassic tectono-stratigraphic evolution of Indochina and adjacent areas: A review with new data

The Neoproterozoic to Early Triassic tectono-stratigraphic evolution of Indochina and adjacent areas can be divided into six mega-episodes: (1) The Neoproterozoic-Early Cambrian mega-episode was characterized by shallow marine environment in the Sino-Vietnam composite terrane. Meanwhile, the different blocks of the Indochina composite terranes were still separated by branches of the Proto-Tethys. Sino-Vietnam and part of Indochina amalgamated along the Proto-Song Ma suture by the end of the Early Cambrian. (2) During the Middle Cambrian-Early Ordovician mega-episode, shallow shelf carbonate deposition prevailed north of the Proto-Song Ma suture with associated strata containing a rich benthic fauna. This contrasts with deep marine and volcanic arc setting in the south of the Proto-Song Ma suture. (3) The Middle Ordovician-Silurian mega-episode was characterized by subduction of the Tam Ky-Phuoc Son Ocean beneath the Viet-Lao terrane in the north and the Kon Tum terrane in the south. This was followed by a collisional orogeny that sutured the Kon Tum terrane with the Viet-Lao and Viet-Cambodia terranes along the Tam Ky-Phuoc Son suture. The hypothetic Po Ko and Chu Sinh sutures are discussed. The collision led to an intra-continental orogeny in the Sino-Vietnam composite terrane. By the end of the mega-episode, a unified Sino-Vietnam-Indochina super-terrane was established. During the latest Silurian-Early Devonian, benthic fauna and flora of the Sino-Vietnam and Indochina composite terranes shared Cathaysian affinity. (4) The Devonian-Tournaisian mega-episode was characterized by an Early-Middle Devonian transgression and a Late Devonian-Earliest Carboniferous regression, except for parts of northern Indochina where deep marine conditions remained. (5) During the Visean-Middle Permian, the Song Ma ocean reopenned in the north of Indochina. Meanwhile in the west, a volcano-plutonic belt formed due to eastward subduction of the Paleo-Tethys under the Indochina composite terrane. (6) The Late Permian-Early Triassic mega-episode was characterized by Emeishan mantle plume related continental rifting, and the Indosinian orogeny resulting from resuturing of the Indochina and Sino-Vietnam composite terranes along the Song Ma suture.